Ice and frost formation can cause severe destruction and massive casualties, such as the disasters resulted from power supply line fault and aircraft icing. Either anti-icing methods (e.g., anti-icing coatings, etc.) or deicing methods (e.g., directly removing ice by force, spraying deicer or heating, etc.) are available to solve these problems. Anti-icing coating is an important and efficient deicing method. Nowadays, researches on anti-icing coatings mainly focus on low surface energy materials, superhydrophobic surfaces and lubricanting coatings.
Polysiloxane with low surface energy is commonly used as anti-icing materials. For instance, NuSil®2180 was presented as a corrosion-resistant anti-icing coating in US 20070254170 (Hoover K L, Watson C R, Putnam J W, Dolan R C, Bonarrigo B B, Kurz P L, Weisse M A. Erosion resistant anti-icing coatings. US 20070254170, 2007). An anti-icing coating with hydrophobic materials as matrix resin and silicone phase change materials as additives was disclosed in U.S. Pat. No. 7,514,017 (Bhamidipati M V. Methods and compositions for inhibiting surface icing. U.S. 7,514,017, 2009). The sol-gel preparation method of an anti-icing coating with ‘interpenetrating network structure’ formed by silicone crosslinking network as matrix was disclosed in U.S. Pat. No. 6,702,953 (Simendinger W H, Miller S D. Anti-icing composition. U.S. Pat. No. 6,702,953, 2004), wherein, ice inhibitor such as polyols was included in the system. Sylgard®184 (Dow Corning Co.), an anti-icing product that can be used as matrix resin, is composed of prepolymer and curing agent. The coating can be obtained by crosslinking of the two components based on hydrosilylation (Alizadeh A, Bahadur V, Shang W, ZhuY, Buckley D, Dhinojwala A, Sohal M. Influence of substrate elasticity on droplet impact dynamics. Langmuir, 2013, 29: 4520-4524).
In addition to low surface energy materials, lubricant is capable of efficiently reducing ice shear strength. For example, Aizenberg et al. developed the concept of slippery liquid-infused porous surfaces (SLIPS), the principle thereof takes use of capillarity. In detail, it was involved in a molecular level slippery surface fabricated by infusing fluorinated fluids immiscible with water into the topological structure of the porous surfaces, resulting in low contact angle hysteresis and ice shear strength (Mishchenko L, Hatton B, Bahadur V, Ashley Taylor J, Krupenkin T, Aizenberg J. Design of ice-free nanostructured surfaces based on repulsion of impacting water droplets. ACS Nano, 2010, 4: 7699-7707). A fabrication method of SLIPS was disclosed in US 20140147627/U.S. Pat. No. 9,121,306, in which perfluorinated compounds or organosilicone were utilized as slippery liquids and absorbed into the rough substrate surfaces, forming a stable lubricant layer. The rough surfaces were obtained by topological structures or porous materials. The substrate materials varied in a wide range, including polymers (e.g., PTFE, epoxy resin, polyester, etc.), metals (e.g., Al, etc.) and inorganic ceramics (Aizenberg J, Aizenberg M, Kang SH, Kim P, Tang KY, Wong TS. Slippery surfaces with high pressure stability, optical transparency, and self-healing characteristics. US 20140147627/US 9121306, 2014).
Fluoropolymers, another kind of low surface energy materials, are often applied in hydrophobic/oleophobic modification, making them promising in the anti-icing field. A three-layer anti-icing coating was disclosed in CN 102205680B, in which the inner layer was composed of organosilicone modified epoxy resin, while the middle layer of polyelectrolytes, and the outer layer of fluorine-silicon modified acrylic ester (Huang C, Li Y, Hu M J, Zhao Y M, Liu X H, Li X L, Huang R H, Luo Y B. An anti-icing coating and its fabrication. CN102205680B, 2014).
Polyhedral oligomeric silsesquioxanes (POSS) are organic-inorganic hybrid molecules with an inorganic core surrounded by eight organic groups. The POSS molecules with eight organic fluorinated groups (fluorinated POSS) could combine low surface energy property with functional and nanosized organic-inorganic hybrid molecules. CN 101029137A disclosed a fluorinated POSS-acrylate block copolymer resin and a synthetic method thereof (Dai L Z, Chen J F, Xu Y T, Deng Y M, Peng X L. Fluorinated POSS-acrylate block copolymer and its preparation method. CN 101029137A, 2007). CN 101875707A disclosed a fluorinated POSS-acrylate copolymer and the preparation of the copolymer coatings which exhibited low-surface-energy and good antifouling properties (Leng S W, Hu W , Wu P. Fluorinated POSS-acrylate copolymer and its synthesis and a coating. CN 101875707A, 2010). Moreover, Mabry et al. had successfully synthesized a novel class of octameric fluorinated POSS, the eight organic groups of which were all nonafluorohexyl, tridecafluorooctyl or heptadecafluorodecyl, respectively. According to their publication, fluorinated POSS was the most hydrophobic crystal materials (Mabry J M, Vij A, Iacono S T, Viers B D. Fluorinated polyhedral oligomeric silsesquioxanes (F-POSS). Angewandte Chemie International Edition, 2008, 47: 4137-4140). Superhydrophobic and superoleophobic surfaces were prepared by spraying heptadecafluorodecyl POSS onto PDMS substrates with microsized columns in regular alignment on the surfaces (Golovin K, Lee D H, Mabry J M, Tuteja A. Transparent, flexible, superomniphobic surfaces with ultra-low contact angle hysteresis. Angewandte Chemie International Edition, 2013, 52: 13007-13011). Meuler et al. blended heptadecafluorodecyl POSS with Tecnoflon rubber or poly(ethyl methacrylate) in Asahiklin solvent, respectively and then spin-coated the solution onto steel sheets. The result showed that the ice adhesion strength decreased obviously compared to that of Tecnoflon rubber surface and poly(ethyl methacrylate) surface. Furthermore, the minimum value of the ice adhesion strength and contact angle hysteresis were 165 kPa and 5.6° respectively, when the mixture consisted of 80 wt % poly(ethyl methacrylate) and 20 wt % heptadecafluorodecyl POSS. As a result, fluorinated POSS was proved to be advantageous in improving icephobic properties of coatings and promising in anti-icing field (Meuler A J, Smith J D, Varanasi K K, Mabry J M, McKinley G H, Cohen R E. Relationships between water wettability and ice adhesion. ACS Applied Materials & Interfaces, 2010, 2: 3100-3110).
Surface wrinkles have been widely used in introducing mico/nano-sized topology structures on films. Jiang et al. prepared wrinkled films by photocuring using epoxy resin as substrate and fluoro-POSS with six thiol groups and two heptadecafluorodecyl acrylate groups (F-POSS-SH) as crosslinker. A bilayer crosslinking system, in which click reaction took place in the top layer, while radical polymerization of C=C in the bulk layer, was formed by the migration of F-POSS-SH. As a result, the formation of controllable wrinkle morphology was triggered by different crosslinking methods in two layers (Gan Y, Jiang X, Yin J. Self-wrinkling patterned surface of photocuring coating induced by the fluorinated POSS containing thiol groups (F-POSS-SH) as the reactive nanoadditive. Macromolecules, 2012, 45: 7520-7526). Regular wrinkle patterns were formed by chemical vapor deposition (iCVD) of a rigid film layer on biaxial pretensioning PDMS substrate (Yague JL, Yin J, Boyce MC, Gleason KK. Design of ordered wrinkled patterns with dynamically tuned properties. Physics Procedia, 2013, 46: 40-45).
There appeared more and more studies on the synthesis and applications of fluorinated POSS, but very few results about applying fluorinated POSS as crosslinker to anti-icing field. Moreover, no research on combining fluorinated POSS with lubricant anti-icing mechanism was reported. In this invention, low-surface-energy fluorinated POSS was introduced into the polysiloxane system and micro/nano-sized surface wrinkles were formed by controlling crosslinking degree. In addition, three-phase interface with ice/lubricant/solid coating surface was obtained due to hydrogen-containing polysiloxane in this system, which comparatively reduced the contact area of ice bulk and solid coating surface. Ice adhesion strength of coatings greatly decreased through the combination of surface wrinkle and lubricanting layer, significantly improving icephobic properties.